Nanoindentation Studies Research Articles

A high Z′ structure of an organic salt with unusually high phase stability, nanoindentation, and mechano and vapo-fluorochromism

Structure (1) with very unique crystal packing and multi-stimuli responsive behaviour is reported. The absence of polymorphism in 1 is supported by experimental studies. Hirshfeld and nanoindentation studies are also reported.

Application of the spherical indenter for determination of the elastic modulus of coatings

In this work a study of nanoindentation of the surface of epoxypolyester-based powder coatings deposited on steel substrates was carried out. The effect of the test method on the identifiable mechanical properties is investigated. The measurement results obtained by using a spherical indenter and a Berkovich indenter are compared. Estimates of reduced modulus of elasticity, Young's modulus and rigidity of coatings are obtained. The experimental data obtained indicate a significant dependence of the determined mechanical properties of the paint and varnish coatings depending on the type of indenter used. In the case of Berkovich indenter, the Young's modulus of coatings (0.6 GPa) is understated in relation to coating properties known from macro experiments (3 GPa). Using a spherical indenter, Young's modulus is overestimated (6.3 GPa).

One-Pot Hydrothermal Preparation of Hydroxyapatite/Zinc Oxide Nanorod Nanocomposites and Their Cytotoxicity Evaluation against MG-63 Osteoblast-like Cells.

In the present study, HAp-ZnO nanorod nanocomposites were successfully prepared using a customized hydrothermal reactor and studied for their compatibility against MG-63 osteoblast-like cells. The crystallinity, morphology, presence of chemical elements, and surface area properties were studied by XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectrum) and N2 adsorption/desorption isotherm techniques, respectively. Further, the mechanical strength and thermal analysis were carried out using the nanoindentation method and thermogravimetric/differential scanning calorimeter (TG/DSC) methods, respectively. Moreover, in vitro biocompatibility studies for the prepared samples were carried out against human osteosarcoma cell lines (MG-63). The crystalline nature of the samples without any impurity phases was notified from XRD results. The formation of composites with the morphology of nanorods and the presence of desired elements in the intended ratio were verified using FE-SEM and EDS spectra, respectively. The TG/DSC results revealed the improved thermal stability of the HAp matrix, promoted by the reinforcement of the ZnO nanorods. The nanoindentation study ensured a significant enhancement in the mechanical stability of the prepared composite material. Finally, it demonstrated that the HAp matrix's mechanical strength and thermal stability were improved by the reinforcement of ZnO, and the cytotoxicity evaluation affirmed the biocompatible nature of the biomimetic hydroxyapatite in the composite.

Estimation of elastic modulus, fracture toughness and strength of 47.5B-derived bioactive glass-ceramics for bone scaffold applications: a nanoindentation study

The knowledge of the mechanical properties of glass–ceramic materials used in bone scaffolds is the key to the optimal design of tissue engineering devices. In this paper, the elastic properties and fracture toughness of silicate bioactive glass-ceramics based on the 47.5B parent composition were quantified for the first time through nanoindentation. Specifically, the effect of sintering temperature was investigated by testing samples sintered at six different temperatures. The samples sintered at higher temperatures exhibited elastic modulus and fracture toughness higher than those of the lower temperature samples. Both properties are comparable with those shown by similar bioactive glasses available in literature, supporting the mechanical suitability of the materials for bone applications. An estimation of tensile strength as a function of flaw size is also provided by means of fracture mechanics approaches.

ATF Claddings after High-Temperature Steam Oxidation: WDS and Nanoindentation Studies to Characterize in-depth Material Changes

After the Fukushima accident in 2011 year, ATF nuclear fuel cladding concept was accelerated to achieve the reactor operation with the new accident tolerant structural materials. However, several designed solutions do not fulfil the accident tolerant concept but particularly increase the corrosion resistance of Zr-cladding tubes at normal operating conditions, so-called “Advaced Technology Fuel, EATF”. Cr-coated zirconium claddings following the first concept, have been the widely tested and the first full Cr-coated fuel rods have been planned to operate in LWR reactor conditions around the 2022 year. Our contribution describes the Cr-coated Zr-%1Nb cladding tube microstructure after high-temperature steam oxidation at 1200°C by means of Scanning Electron Microscopy and nanoindenta-tion methods. The article is focused on WDS line-profile studies of oxygen and chromium diffusion into the Zr-matrix. The increased Cr-diffusion with oxygen is evident causing a change in local me-chanical properties which is well-described by measurements of nanohardness and Young's modulus. In addition, the developed methodology of the WDS & nanoindentation line-analyses was also opti-mized to apply in hot-cell conditions to measure the effect of neutron-irradiation on the different coat-ings and coating/matrix interface.

Syntheses and fabrication of mesoporous styrene-co-methyl methacrylate-graphene composites for oil removal

The current study reports the successful preparation of mesoporous polystyrene-co-polymethyl methacrylate/commercial graphene (PS-r-PMMA/CG) and polystyrene-co-polymethyl methacrylate/reduced graphene oxide (PS-r-PMMA/RGO) composites and their potential application for fast removal of oil from produced water. The copolymer composites were characterized by Fourier-Transform Infrared spectroscopy (FT-IR) Raman spectroscopy, thermogravimetric analyses (TGA), and nano-indentation methods. The copolymer composites were fabricated into mesoporous structures by dissolving the polymer composites in a good solvent, followed by freezing at a very low temperature and subsequently exchanging the solvent crystals with non-solvent at elevated temperatures. The TGA and nano-indentation studies showed that the composites are thermally stable up to 401 °C with enhanced elasticity and hardness values. SEM and BET results showed that the fabricated structures are mesoporous with pore sizes ranging from 35 to 65 nm while the surface area can be as high as 220 m2/g. The fabricated mesoporous copolymer composites exhibit high adsorption capacities for oil from water solutions even at very low concentrations. The demonstrated high adsorption capacities and the excellent recyclability make polymer adsorbents potential candidates for produced water treatments.

Fabrication and Characterization of Free-Standing and Flexible Polyaniline Membranes: Role of Graphene Nanoscrolls

Wearable technologies can contribute to the early and accurate detection of chronic diseases which can be achieved by the integration of biosensors into wearable technologies. However, the challenges associated with the performance of current electrode materials—i.e., flexibility, conductivity, and mechanical stability, made from conducting polymers are preventing their widespread usage. Herein, we report a freestanding and flexible electrode synthesized from polyaniline (PANI) and graphene nanoscrolls (GNS). The PANI-GNS nanohybrid membranes were synthesized via chemical oxidative polymerization and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and four-point probe techniques. FTIR results showed an increase in conjugation length of the PANI after the addition of GNS into the mixture which can be indicative of an enhancement of electrical properties. Nanoindentation studies showed an elastic modulus and hardness of 2.6 GPa and 0.17 GPa, respectively, for PANI-GNS-5 nanocomposite, compared to 1.9 GPa and 0.08 GPa, for pure PANI. This was later confirmed by the four-point probe technique as the addition of GNS increased the conductivity of electrodes up to 9 S/cm at a 5% weight ratio. Moreover, SEM results of the PANI-GNS showed an open porous morphology of the polymer matrix in comparison with pure PANI samples which would readily translate into higher amounts of enzyme immobilization on the surface.

An experimental study on tribofilm formation and endurance with nanolubricants

ABSTRACT This work investigates the formation, endurance and rupture of tribofilms on a honed engine liner subjected to boundary lubrication in a reciprocating Tribometer. Study focuses on the exploration of synergistic effect between ZDDP additive in the oil and two distinctly shaped nanoparticles, Graphene oxide (GO) and detonation nanodiamond (DND), in improving the characteristics of tribofilm. Tested samples were examined by scanning electron microscope and energy dispersive X-ray. The results indicated that the addition of nanoparticles to the base oil with ZDDP accelerates the tribofilm-formation. Although fully developed tribofilms were obtained with both the nanoadditives, the DND based tribofilm was more durable under the dry running conditions. However, P-rich tribofilm formed in the presence of GO showed self-mending characteristics. Nanoindentation studies on the wear tack revealed a 12% increase in elastic modulus and 23% increase in average hardness for the sample tested with DND compared to that of base lubricant.

Comparative nanoindentation study of biogenic and geological calcite

Biogenic minerals are often reported to be harder and tougher than their geological counterparts. However, quantitative comparison of their mechanical properties, particularly fracture toughness, is still limited. Here we provide a systematic comparison of geological and biogenic calcite (mollusk shell Atrina rigida prisms and Placuna placenta laths) through nanoindentation under both dry and 90% relative humidity conditions. Berkovich nanoindentation is used to reveal the mechanical anisotropy of geological calcite when loaded on different crystallographic planes, i.e., reduced modulus Er{104} ≥ Er{108} > Er{001} and hardness H{001} ≥ H{104} ≥ H{108}, and biogenic calcite has comparable modulus but increased hardness than geological calcite. Based on conical nanoindentation, we elucidate that plastic deformation is activated in geological calcite at the low-load regime (<20 mN), involving r{104} and f{012} dislocation slips as well as e{018} twinning, while cleavage fracture dominates under higher loads by cracking along {104} planes. In comparison, biogenic calcite tends to undergo fracture, while the intercrystalline organic interfaces contribute to damage confinement. In addition, increased humidity does not show a significant influence on the properties of geological calcite and the single-crystal A. rigida prisms, however, the laminate composite of P. placenta laths (layer thickness, ∼250–300 nm) exhibits increased toughness and decreased hardness and modulus. We believe the results of this study can provide a benchmark for future investigations on biominerals and bio-inspired materials.

On the Evolution of Nano-Structures at the Al-Cu Interface and the Influence of Annealing Temperature on the Interfacial Strength.

Molecular dynamics (MD) simulations are invoked to simulate the diffusion process and microstructural evolution at the solid–liquid, cast-rolled Al–Cu interfaces. K-Means clustering algorithm is used to identify the formation and composition of two types of nanostructural features in the Al-rich and Cu-rich regions of the interface (i.e., the intermetallic Al2Cu near the Al-rich interface and the intermetallic Al4Cu9 near the Cu-rich interface). MD simulations are also used to assess the effects of annealing temperature on the evolution of the compositionally graded microstructural features at the Al–Cu interfaces and to characterize the mechanical strength of the Al–Cu interfaces. It is found that the failure of the Al–Cu interface takes place at the Al-rich side of the interface (Al2Cu–Al) which is mechanically weaker than the Cu-rich side of the interface (Cu–Al4Cu9), which is also verified by the nanoindentation studies of the interfaces. Centrosymmetry parameter analyses and dislocation analyses are used to understand the microstructural features that influence deformation behavior leading to the failure of the Al–Cu interfaces. Increasing the annealing temperature reduces the stacking fault density at the Al–Cu interface, suppresses the generation of nanovoids which are precursors for the initiation of fracture at the Al-rich interface, and increases the strength of the interface.

Nanoindentation study and theoretical analysis of elastic behavior of single TiO2 nanobelt and nanotube

Based on the theory of plate and shell mechanics, single TiO2 nanoribbon and nanotube were abstracted into a two-dimensional (2D) thin plate model and cylindrical shell model respectively. The mechanical behavior under load in the corresponding working environment was discussed, and the corresponding continuum equivalent mechanical model and mechanical behavior were established and theoretically calculated, respectively. Combined with the measured results of the atomic force microscope (AFM), the theoretical and experimental results are compared to verify the rationality of the theoretical model. Herein, the constitutive equations and solution approaches are given, and the reliability of the theoretical model is confirmed by the measured results of AFM, which could provide an important basis for the application of nanodevices or structures based on TiO2 nanoribbons or nanotubes.

Nanoindentation study of mechanical and wear properties of spark plasma sintered Ti-6Ni-xTiCN composites

In this study, monolithic pure Ti and Ti-6Ni-xTiCN composites were fabricated by the spark plasma sintering method and the mechanical and anti-wear characteristics of the fabricated samples were investigated using the nanoindentation technique. Microstructural and phase analysis of the sintered samples showed the predominance of the α-Ti phase in the unreinforced pure Ti matrix. In addition to the α-Ti phase, in-situ TiN, Ti2Ni intermetallic, and undissolved TiCN phases were detected in the matrix of the composites. Nanoindentation results revealed that the hardness (H), elastic modulus (Er) and elastic recovery index (We/Wt) of the investigated samples increase with increasing reinforcement contents under varying loads of 50 mN, 100 mN and 150 mN. The nanomechanical and anti-wear properties of the analysed samples indicated dependency on the applied indentation load. The Ti-6Ni-xTiCN composites displayed higher H/Er,H3/Er2 and We/Wt ratios that signified better wear and impact resistance than the unreinforced pure Ti. Microstructural integrity, which ensures consistency between the anti-wear characteristics obtained through the nanoindentation technique and the conventional wear testing, was achieved in composites containing TiCN nanoceramic contents up to 10 wt%. Ti-6Ni-10TiCN composite displayed the optimum combination of the nanomechanical and anti-wear properties across the applied loads.

Investigation of a novel sub-surface work hardening phenomenon in micro-turning of Zr-based bulk metallic glass

This study investigates the influence of the micro-turning operation on the subsurface deformation-induced transformation. The variations in nanohardness, shear transformation zone (STZ) volume, and free volume in the machined subsurface of the Zr-based bulk metallic glass (BMG) have been characterized. Nanoindentation studies reveal that the machined subsurface is strain hardened, a unique phenomenon that has not been reported in Zr-based BMG machining. The work-hardened zone extends until a depth of ∼20 μm from the surface. The quantitative evaluation of the deformation-induced hardening has been done experimentally by nanoindentation followed by the free volume characterization via Differential Scanning Calorimetry (DSC). The Shear Transformation Zone (STZ) volume approach has been used to understand the changes in the machined subsurface induced due to microturning. The STZ volume in the machined region is lower than that in the undeformed zone for all the machining conditions investigated in this work. The enthalpy change obtained using DSC analysis for estimating the change in free volume content of the machined regions correlates with the STZ volume.

A review of nanoindentation and related cathodoluminescence studies on semiconductor materials

A review of nanoindentation and related cathodoluminescence studies on semiconductor materials

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Microstructural and nanoindentation study of TaN incorporated ZrB2 and ZrB2–SiC ceramics

This study assessed the sinterability and microstructure of ZrB2-SiC-TaN and ZrB2-TaN ceramics. Spark plasma sintering at 2000 °C and 30 MPa for 5 min produced both ceramics. The relative density of ZrB2 ceramic containing TaN was 95.3%; the addition of SiC increased this value to 98.1%. SiC’s contribution to the elimination of ZrB2 surface oxides was the primary factor in the advancement of densification. The in situ formation of hexagonal boron nitride at the interface of TaN and ZrB2 was confirmed by high-resolution transmission electron microscopy, field emission-electron probe microanalyzer, X-ray diffractometry, and field emission scanning electron microscopy. Moreover, the in situ graphite might be produced as a byproduct of the SiC-SiO2 process, hence boosting the reduction of oxide compounds in the ternary system. The SiC compound had the highest hardness (29 ± 3 GPa), while the ZrB2/TaN interface exhibited the greatest values of elastic modulus (473 ± 26 GPa) and stiffness (0.76 ± 0.13 mN/nm).

Regenerative repair of full thickness skin wound assisted by dual crosslinking percolative gel casting maneuvered alginate hydrogel embedded with honey ghee blend resembles standard cutaneous properties

We report synergism in scarless cutaneous wound repair by alginate hydrogel (HGSAG) embedded with an optimized blend of characterized Jamun honey and characterized indigenously prepared ghee. Thorough screening and characterization of honey and ghee are carried out followed by obtaining a novel dual crosslinking percolative gel casting fabrication method to come up with HGSAG showing superior chemical stability, and mechanical strength (Nanoindentation study; lowest stiffness: 0.71 ± 0.19 μN/nm), and surface morphology (SEM; highest roughness: 0.13 ± 0.04 μm) to other variants. In vitro swelling study and degradation behavior study show intermediate swelling (swelling index: 0.59 ± 0.008 in 98 h) and required restricted degradation (PBS: 73.38 ± 0.55%, DMEM: 83.48 ± 0.69% in 10 days) for HGSAG which is necessary for providing nutrients to cells and in vivo therapeutic efficacy. We observe the remarkable antibacterial efficacy of HGSAG against Staphylococcus mutans and Escherichia coli. This particular substrate also shows decent 3T3 fibroblasts viability, cell-cell communication followed by cell-matrix interaction, and proliferation compared to other variants. Molecular gene expression studies by quantitative RT-PCR technique reveal strong upregulation of collagen I, CD26, and TGF-β3 while downregulation in the case of TGF-β1 which eventually substantiates scarless wound healing potential of HGSAG. Wound closure kinetics is most rapidly and successfully underpinned by HGSAG while compared to other alternatives including marketed healing patches. Regular close monitoring using histopathological studies and real-time imaging by Swept-Source Optical Coherence Tomography of in vivo wound model treated with HGSAG come up with the fascinating result of scarless healing (HGSAG treated epithelial thickness: 62.96 ± 0.67 μm, unwounded akin epithelial thickness: 62.56 ± 0.34 μm) within 12 days of wounding. Thus, the work highlights modified and stabilized alginate hydrogel embedded with honey and ghee blend as a potential scarless full-thickness cutaneous wound healing bio-scaffold.

Atomistic nanoindentation study of Al–Mg intermetallic compounds based on molecular dynamics simulation

In this paper, a 3D molecular dynamics (MD) simulation is performed to investigate the nanoindentation process, the most frequently used technique to measure mechanical properties such as hardness, of three Al/Mg intermetallic compounds, where Mg is the main element added to pure Al. To further improve the understanding of the mechanical response, in this study, we examine the hardness-strength data for three kinds of typical materials, including [Formula: see text]-Al3Mg2 and [Formula: see text]-[Formula: see text][Formula: see text] and [Formula: see text]-[Formula: see text][Formula: see text] phases with different microstructures. In terms of the observed morphologies around the indentations, the influencing variables of the general link between strength and hardness are described. Accordingly, atomic simulations in this paper are performed under the same loading ([Formula: see text]) using a spherical diamond indenter. At both the [Formula: see text]-[Formula: see text][Formula: see text] and [Formula: see text]-[Formula: see text][Formula: see text] phases, we can see that the indenter generates a bigger deformation zone and a greater number of dislocations in the [Formula: see text] direction. The simulation findings show that the microstructure has an impact on the shape of the deformation in each phase. After the deformation process, we get the depth-displacement ([Formula: see text]–[Formula: see text]) curves to describe the mechanical behavior of [Formula: see text]-Al3Mg2, [Formula: see text]-[Formula: see text][Formula: see text] and [Formula: see text]-[Formula: see text][Formula: see text] phases. From the [Formula: see text]–[Formula: see text] curves, we got the radial distribution function, mechanical properties, such as micro hardness, Yield point and maximum load are determined and presented. According to the findings, the chemical composition of these phases has a considerable impact on their characteristics. These [Formula: see text]–[Formula: see text] curves obtained show a rapid increase in loading up to a maximum. The deformation behavior of −Al3Mg2 and −[Formula: see text][Formula: see text] phases under nanoindentation is slightly identical, and they have also a high elasticity limit, the ability to endure deformation and the characteristic of being very ductile and malleable. While [Formula: see text]-[Formula: see text][Formula: see text] phase was shown to be brittle and weak under the same uniaxial nanoindentation loading compared to other phases, it was found that there is a good correlation between the previous simulated studies.

Effect of sulfate attack on the composition and micro-mechanical properties of C-A-S-H gel in cement-slag paste: A combined study of nanoindentation and SEM-EDS

Sulfate attack is a common type of corrosion that results in the deterioration of cementitious materials, but its attacking mechanism on the micro-mechanical properties C-A-S-H gel is still not fully understood. This paper utilizes combined techniques of XRD, nanoindentation and SEM-EDS to investigate the composition and mechanical properties evolution of C-A-S-H gel in cement-slag paste under sulfate attack. It is found that the pozzolanic reaction of slag depletes portlandite and produces AFm, which can act as a buffer for the ettringite formation during sulfate attack. Sulfate ions can adsorb on C-A-S-H gel and cause the its compositional decalcification and dealumination. Slag incorporation can decrease the sulfate adsorption capacity of C-A-S-H gel and moderates its compositional change under sulfate attack. The composition change of C-A-S-H gel induced by sulfate attack is accompanied with its micro-mechanical properties’ degradation, and this degradation is a result of its increasing porosity during decalcification and dealumination but not related with its original composition. The incorporation of slag reduces the decalcification and dealumination of C-A-S-H gel in the paste induced by sulfate attack, thus improving its micro-mechanical properties stability in sulfate attacking environment.

Sulfur-doped graphitic carbon nitride (S-g-C3N4) as an efficient corrosion inhibitor for X65 pipeline steel in CO2- saturated 3.5% NaCl solution: Electrochemical, XPS and Nanoindentation Studies

The present study reports the role of sulfur-doped graphitic carbon nitrides (S-g-C3N4) as a self- assembly corrosion inhibitor for X-65 steel in 3.5% NaCl solution enriched with CO2. The S-g-C3N4 was synthesized via simple pyrolysis and polymerization route. Detailed physiochemical characterization was carried out using XRD, Raman, FTIR, UV, and XPS analysis. Surface analysis such as FE-SEM and AFM studies reveals a uniform coating of S-g-C3N4 over the steel surface. Electrochemical techniques were adopted to investigate the efficiency of S-g-C3N4 on steel corrosion mitigation. Maximum inhibition efficiency of 98% and 94% at concentration of S-g-C3N4 (0.3 wt%) for polarization and impedance methods were achieved. Also, the DFT and MD simulation studies evidenced that S-g-C3N4 forms a protective layer over the steel surface. The excellent inhibition efficiency of the S-g-C3N4 is due to the presence of sulfur heteroatom thus has more affinity towards steel surface. This sulfur doped g-C3N4 could open up new opportunities in corrosion and materials protection area.